The use of CNG (Compressed Natural Gas) as fuel in a combustion system including a vehicle engine is environmentally friendly, generates economic benefits, and is characterized by low emission of toxic materials such as HC, CO, and PM (Particulate Matter), thus leading to almost none of the odors and fumes of exhaust gas. In the present invention, a combustion system includes a vehicle engine, and in some cases, a combustion system other than one for a vehicle is also called a static combustion system, which is distinguished from one for a vehicle, that is, a dynamic combustion system.
In the related art with regard to an exhaust gas purification catalyst for a compressed natural gas vehicle and a purification method thereof, Korean Patent No. 670221 by the present applicant discloses, as an exhaust gas oxidation catalyst for a compressed natural gas vehicle, loaded with noble metal components containing palladium and platinum, a catalyst for improving oxidation activity on exhaust gas from a compressed natural gas vehicle, which is configured such that palladium-impregnated first alumina, platinum-impregnated second alumina, CeO2—ZrO2 composite ceria and nickel oxide are loaded on a ceramic support. Also, as disclosed in Korean Patent No. 1524054 by the present applicant, an exhaust gas oxidation catalyst for a compressed natural gas combustion system, particularly a catalyst for improving oxidation activity on exhaust gas from a compressed natural gas vehicle or static combustion system in excess air, is configured such that palladium-impregnated first alumina, platinum-impregnated second alumina, and a ceria component are loaded on a ceramic support and the first alumina is impregnated with a cocatalyst selected from the group consisting of barium, nickel, lanthanum, samarium and yttrium so as to improve oxidation activity on methane, which is an exhaust gas component from a compressed natural gas vehicle or static combustion system, in excess air.